Combined Cycle Power Plant

• The Combined Cycle Power Plant or combinedcycle gas turbine, a gas turbine generatorgenerates electricity and waste heat is used tomake steam to generate additional electricityvia a steam turbine.

• A Combined Cycle Power Plant produces high power outputs at high efficiencies (up to 55%) and with low emissions. In a Conventional power plant we are getting 33% electricity only and remaining 67% as waste.

• By using combined cycle power plant we are getting 68% electricity.

Inner Workings of a Combined-Cycle Power Plant

• A combined-cycle power plant uses both a gas and a steam turbine together to produce up to 50 percent more electricity from the same fuel than a traditional simple-cycle plant. The waste heat from the gas turbine is routed to the nearby steam turbine, which generates extra power.

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Fig: A Combined Cycle Power Plant

How a Combined-Cycle Power Plant Produces Electricity

Gas turbine burns fuel:

The fast-spinning turbine drives a generatorthat converts a portion of the spinning energyinto electricity.

Heat recovery system captures exhaust:

The HRSG creates steam from the gas turbineexhaust heat and delivers it to the steamturbine.

Steam turbine delivers additional electricity:

The steam turbine sends its energy to thegenerator drive shaft, where it is convertedinto additional electricity.

Advantages of Combined Cycle Power Plant

• The efficiency of the combined cycle plant is better or higher than the turbine cycle or steam cycle plant. The efficiency of combined cycle power plant will be of the order of about 45 to 50%.

• fewer moving parts and less vibration than a reciprocating engine

• very low toxic emissions• runs on a wide variety of fuels• high operating speeds

Disadvantages of Combined Cycle Power Plant

• Higher cost

• longer start-up

• less responsive to power demands

• shrill whining noise.